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%I #7 Mar 17 2019 03:22:59
%S -2,5,16,23,25,40,49,44,52,59,56,57,70,67,77,85,81,89,79,81,91,94,101,
%T 92,91,100,102,103,125,129,137,160,169,166,167,160,157,156,154,145,
%U 160,160,162,168,172,180,181,203,202,209,204,209,213,212,208,215,228,227,237,236
%N n-th non-Chen semiprime minus n-th Chen semiprime.
%C Chen semiprimes: semiprimes m such that m+4 is either a prime or a semiprime.
%F a(n) = A175680(n) - A175634(n).
%p isA175634 := proc(n) isA001358(n) and (isprime(n+4) or isA001358(n+4)) ; end proc:
%p A175634 := proc(n) option remember; if n = 1 then 6; else for a from procname(n-1)+1 do if isA175634(a) then return a; end if; end do: end if; end proc:
%p isA175680 := proc(n) isA001358(n) and not isA175634(n) ; end proc:
%p A175680 := proc(n) option remember; if n = 1 then 4; else for a from procname(n-1)+1 do if isA175680(a) then return a; end if; end do: end if; end proc:
%p A175735 := proc(n) A175680(n)-A175634(n) ; end proc:
%p seq(A175735(n),n=1..120) ; # _R. J. Mathar_, Aug 25 2010
%K sign,less
%O 1,1
%A _Juri-Stepan Gerasimov_, Aug 25 2010
%E Keyword:sign,less set; corrected (87 replaced by 91, 210 replaced by 204) - _R. J. Mathar_, Aug 25 2010. Also corrected by _D. S. McNeil_, Aug 25 2010
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